The prologue preserves the previous frame pointer, establishes a new one, and allocates stack space for local variables. The epilogue restores the stack and frame pointers to their original state before returning.
Prologue
push rbp ; Push previous base pointer to the stack, so it can be restored
mov rbp, rsp ; Set base pointer to the current stack pointer
sub rsp, N ; Subtract stack pointer by N (allocate stack space)Epilogue
mov rsp, rbp ; Restore stack pointer as the base pointer
pop rbp ; Restore base pointer as previous base pointer
retA lot of compilers offers frame pointer omission as an optimization (e.g. GCC’s -fomit-frame-pointer). In this case, we won’t have this complicated prologue/epilogue. When enabled, the compiler may eliminate the frame pointer (rbp) usage for functions that don’t require it, simplifying the prologue and epilogue and potentially improving performance.